That’s really odd. Do you have a smart plug around the house? Or a safe way to check the outlet’s voltage that you are using? Just seems super odd that 2 machines, potentially made months apart have the same fault.
I’m not sure what a 5 or 6% shortage will do to the printer (if anything), but it would be good to know that the issue isn’t a local issue disguised as a printer fault.
Ok. BTW they are lead screws (not ball screws) on these printers.
Mine are black too when I clean them after a few months when the printer asks me for it, even though I use SuperLube silicone grease with PTFE⁽¹⁾ which is translucent white out of the tube.
I don’t know why it becomes black (oxidization under heat and captured microparticles, I guess). Do you guys also get black grease on lead screws?
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¹ There are in fact two variants of this. I use SuperLube 21030, whereas SuperLube 92003 (which is heat resistant) should be better and is the one recommended by Bambu Lab. They also recommend BX-300/F(DF) Series high temperature grease with fluorine and Lucas Oil 10533 White Lithium Grease.
SuperLube 92003 is going dark too 
Welp, seems like my first layer quality went down the drain 
Guess I’ll have to troubleshoot using their Wiki article regarding first layer quality.
Yes it’s normal because of the wear down metal particles and oxidation. Don’t worry too much. Clean it when you want to
Pretty sure it’s due to the brass nut oxidation being worn off with the contact to the screw
Brass nut oxidation, it’ll get ya every time! 
I have used it on 2 separate outlets with the same result unfortunately. Both pulling the proper voltage.
0.28-0.33 is normal for most bambu pla on h2d 0.4 nozzles, it’s the same on hf nozzles as well.
I think you meant to tag someone else’s reply. Mine was about external factors (power/voltage).
@WisestMoose how’s your ambient temp? If it’s cold, try manually turning off the chamber exhaust after starting a job. Some people were having over cooling issues in cold rooms when that top vent opens and pulls cold air over the print.
In all honesty, I am not impressed with the print quality of my H2D either. I have 3 X1C’s and a P1S that all print better than my H2D. I don’t really have the time to go down the rabbit hole troubleshooting it either, which pretty much means it does nothing. A very big $2400 paper wieght… I am not happy about the purchase at this point. When I do try to print with it, it moves and shakes a whole lot more than my X1C’s, which is to be exprected, but yeah, it dances, lol.
The ambient temp is 22-23 degrees Celsius in the room. No drafts.
I have noticed very weir looking z-seams on mainly round objects with the H2D recently. Has somebody a clue what this could be.
The rest of the print looks quite nice.